Punching-tool.



T. MoG-RATH.

PUNUHING TOOL.

APPLIOATION FILED MAR. so, 1906.

994,714, Patented Nov. 24, 1908.

STATES THOMAS McGRATH, or NEW YORK, N. Y.

rUNcHING-roon Specification o! Lettem ratent.

Patented. Nov. ac. woe.

Application filed mi 80,1906. Serial No..808,892.

To all whom it may concern:

Be it known that I, THOMAS MCGRATH, a citizen of the United States, residing at New York, borough of Manhattan, in the county of New York and State of New York, have invented a certain new and useful Punching-Tool, of which the following is a specification.

This invention relates to a unch especially adapted for punching ho es in metal and hard materials.

The object of the invention is to provide a new construction adapted to punch a hole which is'free from jagged or rough edges. The new tool is very simple in construction, and particularly durablerin use, ,it having been found in practice that several thousand holes can be punched by one tool without refacing. or re-sharpening said tool. The punching surface can be easily and quickly ground to again sharpen the-tool. Furthermore, the tool operatesefiiciently in punching thick or heavy metal plates. The new punch will not break in service, and it will not injure the edge of the die with which it cooperates.

In a prior patent 26, 1905, #808,470, have disclosed a punching tool which is provided with a cutting edge and with a recessed or countersunk face, said edge lying in advance of said countersunk end surface of the tool. Practical experience with a tool pf this construction has demonstrated that, it will operate successfully only on soft metals, such as copper, and analogous materials. Furthermore, the patented tool will not unch thick metallicl sheets or plates, nor will it punch hard meta s.

My newly constructed tool, in -contradistinction to the one disclosed in In prior patent aforesaid, has a punching ace extending forwardly of, or rojecting beyond, the cutting edge, and' as t e tool approaches the work, the projecting unching face engages with the metal be ore the unching edge. comes into action, the cutting edge graduallyapproaching the metal, whereby the metal is deflected by the embedding of the punching face therein, the subsequent operation of the cutting ed hole with smooth edges. It as been found that this type of punch produces a hole the anted to me Decemberproducing asheet of metal for the metal surrounding which is not torn'or disrupted radially to anything like the extent as occurs with the punches of the prior art.

In practice I prefer to make'the rojecting punchin surface or face of t e tool, convex or su stantially so, or frusto-conical or substantially so. The tool is preferably made circular in cross section, though it may be of any shape desired, and it has a sharp cutt ngedge, the punching surface projectmg in front of said cutting edge.

in the operation of punching a hole in a metallic sheet, particularly if it is a thick or heavy sheet, the tool ordinarily used is liable to break, or to slip on the surface of the work; and, furthermore, the edges of the hole are rough and irregular, thus male mg it necessary to finish the holes by filing away the rough edges thereof.

The new tool is not open to these objeciZlOIlS. lVhcnthe tool is brought into contact with the work by the pressure exerted by the press, the projecting punching surface of said tool is embedded in the metal before the cutting edge comes into action.

This step of embedding the tool steadies it relatively to the work, and prevents it from sliding on the-surface of the metal. Under the action of the press, the tool operates to 'cut out the metal leaving a hole with a clean cut and well defined periphery.

In using my invention on certain kinds of work 1 emploa center-finder ada ted to extend beyondi he working surfac oFthe' tool or punch, saidcenter finder being movable freely in an upward direction within the tool. Said tool has a bore or passage for the accommodation of the center finder, and the weight of said finder is augmented by the em lo merit of means adapted to adjust the in er for varying the operative ength thereof. Said means consists of one or more nuts screwed on a threaded upper part of the finder andadapted to move or play therewith relative to or within'the tool or 1ts holder.

The center finder projects normally be. yond the working face of the tool in order that the ointed end. of-the finder may engage at tie proper point with the work or purposes of centering the latter below the too or punch. It shoul be explained that it is customary to rule or I purpose of exposing its working end beyond the punch. v

In the drawings Figure l is a side elevation, part1 ,in section, of a punching tool constructs tion; Figs. 2, 3 and 4 are a series of views representing the operation of punchin a ho e in a sheet of hard material; Fig. 5 1s a vertical section through the punchfand the holder therefor to show the position of the center finder therein; Fig. Sis a detail view of the center finder removed from the-tool.

As shown, thepunch A comprises a body ortion, a, prom ed with a forwardly proectin' punching face, 1),relative to the cutting e go 0. The body is, preferably, circular in cross section although this particular" shape is not essential, and the cutting edge, -c, is continuous. This cutting edge 15 back of, or above, the conical punching face, 5,

the latter being bounded said edge a. The

body a, of thetool is enlarged as at d and flared at e, for the purpose at fittin the punch in the ring or gland B, by which the punch is coupled to the holder Q. As shown, the gland B is adapted to-be screwed to the holder C, for the pulpose of attaching the punch' removebly tothe holder, thus enabling the punch to bedetached for the pun ose oft resurfacing the face 7) and sharpening the cutting edge e. Punches of di fierent sizes may be use interchangeably n the holder (3 torthe purpose of punching holes of diderent diameters in the material or work.

In connection with the punch 51,1 prefer to use a'center finder the latter being con structed as shown more particularly by Figs. 5. and 6. 'lhsholder t} has a longitudinal bore or pessa'ge f, and the tool, or unch A has a similar bore or passage g, t e letter i being in alinement with the passage 7, The

. .1; center finder fits loosely in t e passage f, g,

. so as to be free to. move or nley therein lengthwise, the pointed end it :ol said finder being adapted to pass through the lace Z of the punch and to project heyond the punch A, as shown. The secretive length ofthe center finder, adapted tobe exposed beyond the face. l2, may be varied h; adjusting, on

the stern, a hut c, the latter sing held in a determined edjusted positionon said stem by a check nut j. The nuts 2, j, are fitted loosely in the passee f of the holder (3, and the nut l is adapts to test, or he seated, on the upper end of the punch A, whereby the in accordance with the invenfinder and the nuts are free to move longitudinally within the unch and the holder. The adjustment of t e nuts on the center finder Eeua'bles it to be used with punches which vary in length. The nuts augment the weight of the center finder and cause it to move downward,=fquickly, the tool.

It will be understood that the holder C is secured in a power press, in order that the punch A may be operated by power. This punch operates in conjunction with 'a die or ed, indicatedat F inFigs. 2, 3 and 4. Between said punch A and the die or bed F is fed or placed, the work G in the form of a sheet or plate of hard material, such as metal. ;AS the much approaches the work,

the center fin er E first enga es at the proper point with the work, sai finder bemg free to give or yield upwardly on the continuedmovement of the tool. The. face )or end 5 of the punch engages with the metal in advance of the edge 0, as indicated by Fig."2,'an d as the punch continues its movement, said face is embedded in the work, see Fig.3, whereb the punch is prevented ifrom slip ing or ecoming displaced on the work, being thus held firmly in'its working position. The continued movement of the punch toward the die or bed brings the edge 0 into action for the purpose of cutting the metal from the sheet or plate,-

and the punch is thus adapted to force its way through the metal, as indicated by Fig. 4. The result of this 0, oration is that the hole is punched in the p ate in a manner to leave smooth and uniform edges. v

M new punch possesses remarkable durabi 't practical tests having demonstrated that as many as ten thousand holes can be by gravity in punched is; comparatively thick sheets of nietal without resharpening the edge 0 of the tool.

It is menifest that the punch is adapted for many uses,'but it has proved to be of especial utility and value for punching structural iron and steel. v

It will be observed, particularly trom Fig. 5, that the body portion, a, of the punch, and the projectin punch face, 5, unite to form the cutting edge,- (2, the said parts, a and 5,

coming together at an obtuse angle, thereby greatly increasing the strength of sold cuttin edge.

fi ring thus described my invention, what I claim as new and desire to secure by Letters Patent is l. A punchv rovided with a cutting edge and a substantially frusto-conical punching face be inning at said edge and extending forwar y thereof 2. A cuttini out dpunch provided with e cutting edge fiorine by two surisces rneet-;'

ing at an obtuse angle, one of wliich sur- In testimony whereof I have signed my faces extends forwai'd from said cutting name to this specification in the presence of 10 edge to form a punching face.

. two subscribing witnesses: "3. A unch provided with a cutting ed e 5 formed y two surfaces meeting at an o THOMAS B tuse angle, and a substantially frusto-conical Witnesses: unchin face beginning at and extending JAS. H. GRIFFIN, orwardl y of said cutting edge. H. I. BERNHARD. 

